/*
 * Crypto wrapper for internal crypto implementation - modexp
 * Copyright (c) 2006-2009, Jouni Malinen <j@w1.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Alternatively, this software may be distributed under the terms of BSD
 * license.
 *
 * See README and COPYING for more details.
 */

#include "includes.h"

#include "common.h"
#include "tls/bignum.h"
#include "crypto.h"

int crypto_mod_exp(const u8 *base, size_t base_len,
        const u8 *power, size_t power_len,
        const u8 *modulus, size_t modulus_len,
        u8 *result, size_t *result_len)
{
    struct bignum *bn_base, *bn_exp, *bn_modulus, *bn_result;
    int ret = -1;

    bn_base = bignum_init();
    bn_exp = bignum_init();
    bn_modulus = bignum_init();
    bn_result = bignum_init();

    if (bn_base == NULL || bn_exp == NULL || bn_modulus == NULL ||
            bn_result == NULL)
        goto error;

    if (bignum_set_unsigned_bin(bn_base, base, base_len) < 0 ||
            bignum_set_unsigned_bin(bn_exp, power, power_len) < 0 ||
            bignum_set_unsigned_bin(bn_modulus, modulus, modulus_len) < 0)
        goto error;

    if (bignum_exptmod(bn_base, bn_exp, bn_modulus, bn_result) < 0)
        goto error;

    ret = bignum_get_unsigned_bin(bn_result, result, result_len);

error:
    bignum_deinit(bn_base);
    bignum_deinit(bn_exp);
    bignum_deinit(bn_modulus);
    bignum_deinit(bn_result);
    return ret;
}
